how to make rust-analyzer run on the virtual filesystem instead of on write

[MangoIV]

Hi! Since I've been using rust-analyzer I was plagued by slow feedback speed - the main issue being that rust-analzyer only updates e.g. type errors after a write and thus takes a full cycle to go via the disk.

Every time I was asking people what I was doing wrong, they just told me this is the expected behavior and "rust is a complex language".

I'm highly doubtful that is the case though.

Other language servers usually keep a virtual filesystem that is regularly synced with the disk but the happy path is just keeping it in sync by applying the changes in the LSP messages and not requiring to save the buffer contents for a new check to happen.

What do I actually have to do to get this behavior with rust-analyzer?

[MangoIV]

This is mainly a concern wrt speed - my editor may run hooks etc. before actually writing to disk and then there's the additional delay of reading the file from disk again and so on - just going via the RPC should typically be magnitudes faster.

[MangoIV]

wow this is really not possible:
#3107

[lnicola]

We don't support all the errors, but we have a bunch of settings you can tweak to see some of them.

[MangoIV]

For me type errors are the most important ones. The rest I don’t really care about when programming

[lnicola]

Using:

  "editor.semanticTokenColorCustomizations": {
    "rules": {
      "unresolvedReference": "#ff0000",
      "*.unsafe:rust": "#eb5046"
    },
    "rust-analyzer.diagnostics.experimental.enable": true

Of course, the experimental diagnostics are disabled for good reasons (false positives).

[MangoIV]

thanks, I'll try it out
why are these all under semanticTokenColorCustomizations?